Fluid transport systems are well known and used in a number of applications. For example, heated fluids, such as melted chocolate, candy, or waxes, may be transported from one station to another during a manufacturing process. Other fluids, such as milk or beer, may be cooled and transported through conduits in a facility. Viscous materials, such as soap, lubricants, or food sauces, may require thermal treatment before being moved through a machine or facility.
One specific application of transporting a thermally treated fluid in a machine is the transportation of ink that has been melted from a solid ink stick in a phase change printer. Solid ink or phase change ink printers conventionally use ink in a solid form, either as pellets or as ink sticks of colored cyan, yellow, magenta and black ink, that are inserted into feed channels through openings to the channels. Each of the openings may be constructed to accept sticks of only one particular configuration. Constructing the feed channel openings in this manner helps reduce the risk of an ink stick having a particular characteristic being inserted into the wrong channel. U.S. Pat. No. 5,734,402 for a Solid Ink Feed System, issued Mar. 31, 1998 to Rousseau et al.; and U.S. Pat. No. 5,861,903 for an Ink Feed System, issued Jan. 19, 1999 to Crawford et al. describe exemplary systems for delivering solid ink sticks into a phase change ink printer.
After the ink sticks are fed into their corresponding feed channels, they are urged by gravity or a mechanical actuator to a heater assembly of the printer. The heater assembly includes a heater that converts electrical energy into heat and a melt plate. The melt plate is typically formed from aluminum or other lightweight material in the shape of a plate or an open sided funnel. The heater is proximate to the melt plate to heat the melt plate to a temperature that melts an ink stick coming into contact with the melt plate. The melt plate may be tilted with respect to the solid ink channel so that as the solid ink impinging on the melt plate changes phase from solid to liquid, it is directed to drip into the reservoir for that color. The ink stored in the reservoir continues to be heated while awaiting subsequent use.
Each reservoir of colored, liquid ink may be coupled to a print head through at least one manifold pathway. The liquid ink is pulled from the reservoir as the print head demands ink for jetting onto a receiving medium or image drum. The print head elements, which are typically piezoelectric devices, receive the liquid ink and expel the ink onto an imaging surface as a controller selectively activates the elements with a driving voltage. Specifically, the liquid ink flows from the reservoirs through manifolds to be ejected from microscopic orifices by piezoelectric elements in the print head.
A number of known methods, such as variable displacement or peristaltic pumps, exist for pumping fluid from one station to another station through a conduit. Another transport method is the use of a compressor conduit disclosed in the patent cross-referenced above. While these various methods may be effective for transporting fluid through a conduit, they do not regulate the temperature of fluid being transported through the conduit. In some applications, fluid is transferred from one location to another at sufficient volume or flow rate that temperature regulation during transit is not required. Delivery of hot water through plumbing in a home or office is such an example. Other applications, however, require that transported fluids be maintained within a temperature range. In still other applications, the volume of fluid being transported or the flow rate of the transported fluid is sufficiently low that heat may be lost or gained during transit. In these applications, the addition or loss of heat during transport may adversely affect the usefulness of the fluid at the receiving station. Therefore, temperature regulation of thermally treated fluids in some applications is a relatively important aspect of the system's effectiveness.
In applications where temperature of a transported fluid is important, all or portions of a pump may be heated or cooled. Such heating or cooling, however, requires time for the initial pump temperature to be reached at system initialization or during recovery from a standby condition that may occur during operation of the system. In applications where availability of a system is time critical, waiting for the pump to reach the initial temperature may be unacceptable. Maintaining the pump at or near the initial temperature may result in excessive energy consumption. Other approaches to maintaining fluids transported in conduits at temperatures different than ambient conditions are required.